1. Field of the Invention
The present invention relates to a superabrasive setting method for mounting superabrasive grains on a manufacturing mold in order to arrange superabrasive grains on a grinding surface of a rotary grinding tool such as grinding wheel, truing tool, dressing tool or the like in manufacturing the rotary grinding tool.
2. Discussion of the Related Art
In the manufacturing of a rotary grinding tool such as grinding wheel, truing tool, dressing tool or the like, it is often the case that a grinding surface of the grinding tool are formed by the use of superabrasive grains such as diamond, CBN (Cubic Boron Nitride) or the like. In this case, the grinding tool should have superabrasive grains arranged uniformly so that the grinding surface is able to grind a workpiece without any local imbalance in grinding operation. To this end, in manufacturing grinding tools, there is utilized a so-called “grain transfer method”, wherein superabrasive grains arranged on an internal surface of a female-type manufacturing mold are transferred onto an external grinding surface of a male-type grinding tool, while superabrasive grains arranged on an external surface of a male-type manufacturing mold are transferred onto an internal grinding surface of a female-type grinding tool.
For example, in Japanese unexamined, published patent application No. 56-163879, an adhesive is applied to an internal surface of a female-type mold as a manufacturing mold for a grinding tool, a net having a mesh size which is somewhat larger than the grain size of diamond abrasive grains is set on the internal surface of the female-type mold, and the diamond abrasive grains are distributed over the net so that diamond abrasive grains are distributed and secured in a grid pattern at space intervals wherein a suitable clearance is secured between each abrasive grain and the next thereto. Therefore, only the diamond abrasive grains which dropped into the mesh holes of the net can be adhered and retained with the adhesive, while other diamond abrasive grains remaining on the net are not adhered. As a consequence, diamond abrasive grains can be arranged regularly at a predetermined distribution density with one diamond abrasive grain set in one mesh hole.
Arranging diamond abrasive grains in a grid pattern as described in the Japanese patent application is very effective in distributing diamond abrasive grains simply and uniformly.
However, it is often the case that the mounting surfaces of the manufacturing mold include a taper surface, a rounded surface, an end surface and the like. Therefore, if it is tried to make arrangement on any of these surfaces in a grid pattern, diamond abrasive grains align consecutively in the circumferential direction at four areas of 90-degree intervals due to the fact that one or the other side of the grid pattern becomes parallel to the circumferential direction of the manufacturing mold and at another four areas of 90-degree intervals spaced through an angle of 45 degrees from the first-mentioned four areas due to the fact that either one of diagonal lines of the grid pattern becomes parallel to the circumferential direction. In a grinding tool which is made by the use of such a manufacturing mold, a problems arise in that grinding accuracy is deteriorated because there occur either one of phenomena that abrasive grains behind in the rotational direction of those making consecutive grain lines do not contribute to grinding work, that some of the abrasive grains are delayed in abrasion from others and that much metal removal takes place at each of portions on a workpiece which are brought into contact with those portions making consecutive grain lines of a grinding tool.